The reinforced gradient concrete beams consist of normal and high strength concrete, in which the compressed zone is made of high strength concrete, and the tensile one is made of normal strength concrete. Experiment on these simply supported beams with two-point loading was carried out, and the test results of strains and deflections of the beams under short-term load were verified and compared with those of nonlinear analysis. It revealed that the average strain at the outer fiber in the compressive zone increased linearly with the increase of external loading. Thus, the general coefficient of average compressive strain at the outer fiber was introduced, and its calculated equation was proposed. Based on the analysis of crack development and curvature of cross section, the calculation method on the immediate and long-term stiffness was proposed for the reinforced gradient concrete flexural member with rectangle section.